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In normal respiration the air passes freely in and out through the gauze and the tubes E and D. When artificial respiration is necessary all that is needed is to start the apparatus and the air going through the small tube (sm) enters the trachea with sufficient velocity to go well down into the lungs. With this device it is not necessary to closely approximate the volume of the normal tidal air, because any excess escapes at once through O without causing undue pressure in the lungs. An excess of air is therefore always desirable. I have found that four different sizes of trachea cannula suffice for our needs. This, however, requires only a variation in size of the trachea end of the cannula. These different sizes can be made, therefore, so that the anesthetic cone will fit each of them.

This device commends itself because of its simplicity, its effectiveness, its cheapness. and the ease of manipulation.

STANFORD UNIVERSITY, CALIFORNIA

J. R. SLONAKER

THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

SECTION F-ZOOLOGY

THE Convocation Week meetings of Section F (Zoology) of the American Association for the Advancement of Science were held in conjunction with those of the American Society of Zoologists at Chicago, Illinois, December 28, 29 and 30, 1920. At the business meeting of the Section, Professor M. F. Guyer was elected member of the council. Professor H. W. Rand was elected secretary of Section F for five years. Professor C. C. Nutting was appointed member of the general committee, and Professor M. M. Metcalf, member of the section committee for five years.

The sectional committee nominated Professor C. A. Kofoid, of the University of California, as vice-president of the Section for the ensuing year. The officers for the Toronto meeting will be: Vice-president-C. A. Kofoid, University of

California.

Retiring Vice-president-John Sterling Kingsley, University of Illinois.

Secretary-Herbert W. Rand, Harvard Univer

sity.

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Member of the Council-M. F. Guyer, University of Wisconsin.

Member of the General Committee-C. C. Nutting, University of Iowa.

Members of the Sectional Committee in addition to the officers above: Vice-president, St. Louis, W. M. Wheeler (1 year); V. E. Shelford (2 years); Herbert Osborn (3 years); H. B. Ward (4 years); M. M. Metcalf (5 years); H. V. Neal, Preceding Secretary; Ex-officio, W. C. Allee, secretary American Society of Zoologists.

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The address of the retiring vice-president of Section F, Professor William Morton Wheeler, of Harvard University, upon "The organization of research, was delivered at the Biologists' smoker at the Ida Noyes Hall, Tuesday evening, December 28, at 8 o'clock. The address attracted an unusually large audience.

Under the rules of the association all arrangements for the program of the meetings were in the hands of the executive committee of the American Society of Zoologists. There were more than ninety papers on the program and it became necessary consequently to divide the program into two sections on Wednesday, the twenty-ninth, meeting simultaneously in the Harper Library and Room 14, Zoology Building.

The "popular interest'' session of the meetings was a symposium on Fertilization, held in the Harper Library, at ten o'clock, on Thursday morning, December thirty. Papers were presented by C. A. Kofoid, F. R. Lillie, E. E. Just, O. C. Glaser, C. E. McClung (excused at personal request) and D. H. Tennant.

The attendance upon all of the meetings was so great as to tax the capacity of the rooms in which they were held. H. V. NEAL, Secretary

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SCIENCE

FRIDAY, JANUARY 28, 1921

CONTENTS

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ELECTRIFICATION OF WATER AND OSMOTIC FLOW1

I

THE exchange of water and solutes between the cell and the surrounding fluid is one of the important factors in the mechanism of life, and a complete theory of the osmotic flow is therefore a postulate of biology. It was a marked advance when the experiments of Pfeffer and de Vries led van't Hoff to the formulation of the modern theory of osmotic pressure. According to this theory the molecules of the solute behave like the molecules of a gas in the same volume and at the same temperature, and the gas pressure of the solute measures the "attraction" of a watery solution for pure water through a strictly semipermeable membrane. Yet it is obvious to-day that in a liquid the electrical forces between solvent and solute must play a rôle and no adequate provision is made for these forces in van't Hoff's law. Traube rejected van't Hoff's theory altogether, suggesting instead that the osmotic flow was from the liquid with lower to the liquid with higher surface tension (and higher intrinsic pressure).

Tinker has shown that van't Hoff's theory for osmosis holds strictly only in the case of ideal solutions, i.e., when the process of solution occurs without heat of dilution and change in volume, but that in the case of non-ideal solutions Traube's ideas explain the deviations from the gas law which are bound to occur. When two different ideal solutions containing equal numbers of particles of solute in equal volume are separated by a strictly semipermeable membrane, equal numbers of molecules of water will diffuse simul

1 Presidential address prepared for the Chicago meeting of the American Society of Naturalists, December 30, 1920.

taneously in opposite directions through the membrane and no change in volume will occur. When, however, the same experiment is made with two non-ideal solutions containing equal numbers of molecules in equal volume, the result is different. As Tinker

has demonstrated mathematically, in this case the flow of water must be from the solution having the lower intrinsic pressure and lower surface tension to the solution with higher intrinsic pressure and higher surface tension. This is what Traube claims, and his theory explains therefore, as Tinker points out, the deviations from the gas law in the case of non-ideal solutions, but it does not prove that the gas law of osmotic flow does not hold in the case of ideal solutions and Traube's theory can not therefore replace van't Hoff's theory.

II

There is a second group of forces not taken into consideration in van't Hoff's law, namely the influence of the chemical nature of the membrane on the solvent. These forces become noticeable when the membrane separating the solution from the pure solvent is not strictly semipermeable. When water is in contact with a membrane it undergoes as a rule an electrification and this electrification of the particles of water plays a great rôle in the rate of the osmotic flow when the solution into which the water diffuses is an electrolyte.

The assumption that water diffusing through a membrane is as a rule, electrified, is justified by a large number of observations. Quincke demonstrated that when water is pressed through capillary tubes it is found to be electrically charged (the sign of charge. being more frequently positive); while the tube has the opposite sign of charge, e.g., negative, when the water is positively charged. When two solutions of weak electrolytes are separated by a membrane (which may be considered as a system of irregular capillary tubes) an electric current causes water to migrate to one of the two poles, according to the sign of its charge. By this method of so-called electrical endosmose it can be shown

that water diffuses through collodion membranes in the form of positively charged particles. Collodion bags, cast in the shape of Erlenmeyer flasks, are filled with a weak and neutral solution of an electrolyte, e.g., M/256 Na,SO,, and dipped into a beaker filled with the same solution of M/256 Na,SO. The opening of the collodion bag is closed with a rubber stopper perforated by a glass tube serving as a manometer. When a platinum wire, forming the negative electrode of a constant current, is put through the glass tube into the collodion bag while the other pole of the battery dips into the outside solution, the liquid in the glass tube rises rapidly with the potential gradient between the two electrodes. The water therefore migrates through the collodion membrane in the form of positively charged particles. The writer has made a number of experiments concerning the osmotic flow through collodion membranes, and it is the purpose of this address to give a brief survey of the results.

III

When a collodion bag is filled with a solution of a crystalloid, e.g., sugar or salt, and dipped into a beaker containing pure water, the pure water will diffuse into the solution and the level of liquid in the capillary glass tube serving as a manometer will rise. At the same time particles of the solute will diffuse out of the bag (except when the solute is a protein solution or a solution of some other colloid). The concentration of a crystalloid solute inside the collodion bag will therefore become constantly smaller until finally the solution is identical on both sides of the membrane. Nevertheless the relative force with which a given solution inside the collodion bag "attracts" the pure water into which the bag is dipped can be measured by the initial rise in the level of water in the manometer, before the concentration of the solution has had time to diminish to any great extent through diffusion. Since in the

2 Loeb, J., J. Gen. Physiol., 1918-19, I., 717; 1919-20, II., 87, 173, 273, 387, 563, 659, 673.

first minutes accidental irregularities are liable to interfere with the result, we measure the rise in the level of liquid in the manometer during the first 20 minutes.

If the initial rise of level of liquid in the solution is thus measured it is noticed that it occurs approximately in proportion with the concentration of the solution when the solute is a non-electrolyte. The rate of diffusion of pure water into a solution of cane sugar through a collodion membrane is therefore approximately a linear function of the concentration of the solute within the limits of O and 1 M. This is what we should expect on the basis of van't Hoff's theory of osmotic pressure.

If, however, a watery solution of an electrolyte is separated from pure water by a collodion membrane, water diffuses into these solutions as if its particles were positively charged, and as if they were attracted by the anion of the electrolyte in solution and repelled by the cation with a force increasing with the valency of the ion (and another property of the ion to be discussed later).

Pure water diffuses into a M/128 solution of NaCl through a collodion membrane more rapidly than it diffuses into a M/64 solution of cane sugar; water diffuses into a M/192 solution of Na,SO, or Na, oxalate still more rapidly than into a M/128 solution of NaCl; and into a M/256 solution of Na, citrate water diffuses more rapidly than into a M/192 solution of Na,SO,, and into a M/320 solution of Na,Fe(CN), still more rapidly than into a M/256 solution of Na, citrate. Assuming complete electrolytic dissociation of the electrolytes in these cases, the influence of the five solutions mentioned should be identical according to van't Hoff's theory. We notice, instead, that the "attraction" of the solutions for water increases with the valency of the anion. This is true for all neutral solutions of salts contained in a collodion bag, regardless of the nature of the cation.

If a collodion bag containing a neutral solution of a salt with bivalent cation, e.g., M/192 CaCl, or MgCl2, or with a trivalent

cation, eg., M/256 LaCl,, is dipped into a beaker with pure water we notice no rise in the level of water in the manometer. In solutions with bivalent or trivalent cations the repulsion of the cation equals or exceeds therefore the attraction of the anion for the positively charged particles of water diffusing through the pores of the collodion membrane. Hence we conclude from these (and numerous similar) experiments that the particles of water diffuse through a collodion membrane as if they were positively charged and as if they were attracted by the anion of an electrolyte and repelled by the cation with a force increasing with the valency of the ion.

It seemed of interest to find that concentration of a cane sugar solution which just suffices to prevent the diffusion of water into a given solution of an electrolyte. Into each of a series of beakers, all containing the same neutral salt solution, e.g., M/192 Na,SO4, was dipped a collodion bag containing a cane sugar solution of different concentration, from M/128 to 1 M, and it was observed in which of these sugar solutions the level in the manometer rose during the first 10 minutes, in which it fell, and in which it remained constant. It was found that the cane sugar solution which was just able to balance the

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attraction" of the M/192 solution of Na,SO, for water had to have a concentration of about or over M/4. If the gas pressure effect alone determined the relative attraction of the two solutions for water the concentration of the sugar solutions required to osmotically balance the M/192 solution of Na,SO, should have been M/64 (or slightly less). Hence the sugar solution balancing osmotically a M/192 Na2SO, solution was found to be 16 times more concentrated than the theory of van't Hoff demands. This high concentration of cane sugar was needed to overcome the powerful "attractive" influence of the anions of a M/192 solution of Na,SO, for the positively charged particles of water. Table I. shows the results of a few such experiments. The solution of the electrolyte was in these experiments always theoretically isosmotic with a M/64 cane sugar solution (on the assumption of complete electrolytic dissociation). The data contained in Table I. have only a qualitative value since no attempt at an exact determination of the concentration of the balancing sugar solutions was made. The data show, however, that the "attraction" of M/128 KCl for positively charged particles of water is eight times as great, that of K2SO, sixteen times as great, and that of M/256 K, citrate almost forty-eight times as great as that of M/64 cane sugar; while the "attraction" of a M/192 solution of a salt with a bivalent cation and monovalent anion, like MgCl2, for water is not greater than that of a M/64 solution of cane sugar.

4

These experiments then prove that the rate of diffusion of water from the side of pure water through a collodion membrane into a solution of an electrolyte increases with the valency of the anion and diminishes with the valency of the cation. They give also a rough idea of the relative influence of these ions upon the rate of diffusion of positively charged water through the pores of the collodion membrane from the side of pure water to the side of the solution.

A second fact brought out in these experiments was that the relative influence of the oppositely charged ions of an electrolyte in

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solution upon the rate of diffusion of positively charged water from the side of pure water to the side of the solution is not the same in all concentrations. Beginning with the lowest concentrations the attractive" effect of the anion for positively charged water increases more rapidly with increasing concentration than the "repulsive" effect of the cation until the concentration of the electrolyte is about M/256; from then on the "repulsion" of the cation upon positively charged water increases more rapidly than the "attractive" effect of the anion. As a consequence we can say that in concentrations of neutral salts between M/256 and M/8 the "attraction" of the solution for water diminishes with increasing concentration. This is the reverse of what we should expect if the gas law alone determined the attraction of water by solutions of electrolytes. When the concentration of the solution is M/8, the apparent electrostatic effects of the ions upon the positively charged particles of water disappear and for concentrations above M/8 the curves for the attraction of water by electrolytes and by sugar solutions show less differ

ence.

We have already mentioned the fact that the valency of the ion is not the only quantity which determines its influence on the rate of diffusion of water through a collodion membrane. In addition to the valency (or the number of electrical charges) a second quantity of the ion enters which may be designated provisionally as the influence of the radius of the ion. In the case of monovalent and monatomic cations the retarding influence on the rate of diffusion of positively charged particles of water through the collodion membrane from the side of pure water into a solution increases inversely with the radius of the ion, namely in the order Li > Na > K > Rb, where the retarding effect is greatest in the case of Li and least in the case of Rb; while in the case of monatomic monovalent anions the accelerating effect upon the rate of diffusion of positively charged particles of water from the side of pure water through the membrane into the

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